The SRB2 gene is a suppresser of translation of the carboxy-terminal domain of the largest subunit of RNA polymerase II (CTD) in yeast, and the corresponding protein is stably associated with this enzyme in a large multi-protein complex. The SRB2 gene product was expressed in E. coli and purified to homogeneity and the identity of the recombinant protein was studied by mass spectrometry. Attempts to obtain biologically active SRB2 for protein-protein interaction and structural studies are underway.